The present invention relates to an improved solenoid valve for regulating the fuel supply pressure of an internal combustion engine.
In modern engine fuel supply systems, a high-pressure pump supplies the fuel to a distributor or so-called xe2x80x9ccommon railxe2x80x9d which supplies the various engine cylinder injectors; and the fuel pressure in the distributor is normally controlled and maintained constant by means of a solenoid valve controlled by a pressure sensor to drain any surplus fuel supplied by the high-pressure pump back into the tank. The solenoid valve comprises a feed conduit communicating with the delivery conduit of the high-pressure pump; and a shutter controlled by an electromagnet and cooperating with a seat in the feed conduit.
In one known pressure regulating solenoid valve incorporated in a radial-piston pump, the shutter is defined by a ball controlled by the end of a stem on the electromagnet armature, and which cooperates with a conical sealing seat at one end of the feed conduit.
On account of dirt, e.g. metal particles, between the ball and the conical sealing seat, the above solenoid valve is subject to sealing problems resulting in a fall in pressure and, hence, malfunctioning of the supply system. And, on account of the very high operating pressure involved, e.g. around 1400 bar, ordinary filtration means inserted inside the feed conduit also result in a fall in pressure in the feed conduit.
It is an object of the present invention to provide an extremely straightforward, reliable pressure regulating solenoid valve designed to eliminate the aforementioned drawbacks typically associated with known solenoid valves.
According to the present invention, there is provided a solenoid valve comprising a fuel feed conduit, and a shutter controlled by an electromagnet and cooperating with a seat located in said conduit; and characterized by comprising fuel filtering means housed in said conduit to prevent particles of dirt from getting between said seat and said shutter, with no excessive reduction in fuel pressure.
In particular, in a solenoid valve in which the seat is conical and located at one end of said conduit, and the shutter comprises a ball cooperating with said conical seat, the filtering means comprise a metal plate having a number of holes and fixed to another end of the feed conduit.